Why is my heating system undersized?

One common cause of undersized heating systems is an incorrectly defined compact schedule. Schedules are used to define the operation of equipment, lighting, heating but also sizing. It should normally be switched off for the heating design during the WinterDesignDay. A correct form for a compact schedule used for controlling internal gains, equipment, and lighting during heating design is as follows:

Schedule:Compact,

Schedule: Office_Lighting,

Fraction,

Through: 31 Dec,

For: Weekdays SummerDesignDay,

Until: 06:00,      0,

Until: 18:00,      1,

Until: 24:00,      0,

For: Weekends,

Until: 24:00,      0,

For: Holidays WinterDesignDay AllOtherDays,

Until: 24:00,      0;

Note that the entire WinterDesignDay is set to 0 which means it is switched off.

If the schedule had been switched on (value above 0) for the winter design day, the size of the heating system would have been calculated based on the existence of the heating effect of the internal gains. This would lead to the heating system being undersized.

See also:

Schedules Design And Sizing Simulations

Compact Schedules